In architecture, a core is a vertical void in a building that can serve a few different purposes. A circulation core is the vertical grouping of an elevator, stair, or pair of the two. A core can also refer to a service core that is vertically continuous throughout the building. If you look at a series of floor plans of a building, you may be able to spot the core by finding the continuous program at the same spot on each floor—for example, the size and location of the stairs should generally stay the same for many levels.